Method for controlling defect of optical disk, optical disk recording device, and optical disk reproducing device

ABSTRACT

An optical disc recording apparatus ( 1 ) includes a system control unit ( 14 ) that judges whether main information and sub information which is recorded by being superimposed on said main information, relocates and records the main information or the sub information, or the main information and the sub information in a replacement area, when it is judged to be a defective area, and registers information in a defect management area in the optical disc, the information associating the defective area with the replacement area to which said defective area is relocated.

TECHNICAL FIELD

[0001] The present invention relates to an optical disc defectmanagement method, an optical disc recording apparatus and an opticaldisc reproduction apparatus, and more particularly to an optical discdefect management method, an optical disc recording apparatus and anoptical disc reproduction apparatus for recording sub information bysuperimposing it on main information.

BACKGROUND ART

[0002] Optical discs represented by DVDs (Digital Versatile/Video Discs)are commonly used media capable of storing a large amount of digitaldata such as AV (Audio Video) data and computer data. For example,high-quality video which is over two hours in length is recorded onread-only optical discs for sale. In order to prevent such digitalcopyrighted works from being illicitly copied onto other recordingmedia, a method known as content encryption is employed (See “NikkeiElectronics” Nov. 18 (1996): 13˜14).

[0003] In the above method, compressed digital content such as movies isencrypted by the use of three-layered secret keys (title key, disc key,and master key) and recorded in a user information area accessible by auser. Of these secret keys, the master key, which is most important ofall, is notified only to a licensed authorized manufacturer, while thedisc key and the title key required for each DVD and title are encryptedon the basis of the master key, and stored in a control information areainaccessible by a user. This prevents a user's access to the secret keysrequired for decryption, and therefore an unauthorized copying such asby means of file copying cannot be carried out.

[0004] However, the above method allows encrypted content to bedecrypted and reproduced by ordinary reproduction apparatuses, when thewhole contents of a recording area including the control informationarea in which the secret keys are recorded, is illicitly copied ontoanother optical disc.

[0005] In response to this problem, there is a method, as shown in FIG.1, for recording sub information onto an optical disc 2000, on whichmain information such as digital content is stored, by means of phasemodulation to displace standard edge positions of recording marks 2001that constitute the main information in the track direction by a minuteamount (See Japanese Laid-Open Patent application publication No.2001-357533). FIG. 2 is a timing chart showing major signals that areused in the above method at the time of recording. According to thismethod, a modulated channel signal C6 is obtained by means of phasemodulation in which a channel signal C2 which constitutes maininformation is advanced by a minute amount when a PE modulated signalC5, which is obtained by performing PE modulation on a result ofcarrying out exclusive OR between a random number sequence C4 and subinformation to be recoded, is “H”, whereas the channel signal C2 isdelayed by a minute amount when the PE modulated signal C5 is “L”.According to such modulated channel signal C6, main information and subinformation are recorded on an optical disc as modulated recording marksC7. In other words, main information and sub information are recordedonto an optical disc by means of phase modulation in which an edge of astandard recording mark C3, which constitutes the main information, isadvanced by a minute amount in the track direction when the PE modulatedsignal C5 is “H” and is delayed by a minute amount in the trackdirection when the PE modulated signal C5 is “L”. Accordingly, since subinformation superimposed on the edges of recording marks cannot becopied even if the whole contents of a recording area including thecontrol information area is illicitly bit-copied onto another opticaldisc, it becomes impossible for an ordinary reproduction apparatus andthe like to decrypt an illicitly copied optical disc, by recordinginformation including secret keys as sub information.

[0006] However, the above existing technique is not capable of verifyingwhether sub information is normally recorded or not, although it iscapable of verifying whether main information is normally recorded ornot. Thus, there might arise a problem that even if main information isnormally recorded, sub information which is supposed to be superimposedin the same area, has failed to be recorded. For example, in the casewhere a content decryption key is recorded as sub information, when anarea is reproduced in which only main information is recorded normallyand in which sub information failed to be recorded normally, it isimpossible to decrypt the encrypted content because the sub informationcannot be reproduced normally.

[0007] Furthermore, in the existing technique, defect management isconducted, for example, in accordance with the linear replacementalgorithm and the like, which is one of the defect management processesintended for DVD-RAMs, when an area is judged to be a defective areawhere main information cannot be recorded normally. In the linearreplacement algorithm, when a defective area is found at the time ofverifying recorded information, such area is relocated to a spare areawhich is provided in advance within an optical disc user area. Then, therespective top sector numbers of such defective area and itscorresponding replacement area are registered and managed as an entrypair in a secondary defect list (SDL) which exists in a lead-in area anda lead-out area of an optical disc. Moreover, the above defective areaand replacement area are provided in a unit of ECC block (16 sectors)and relocation processing is performed on an ECC block basis.

[0008]FIG. 3 is a conceptual diagram showing an existing linearreplacement processing. As shown in FIG. 3A, inside an optical disc are:a user area 1701 in which main information is stored by formingoptically-readable recording marks and in which sub information isstored by displacing their recording mark edges by a constant minuteamount; a spare area 1702 intended for relocation used when the userarea 1701 is a defective area; and, as shown in FIG. 3B, a secondarydefect list (SDL) 1703 for managing the respective top sector numbers ofa defective area and a replacement area as an entry pair when suchdefective area is relocated to the replacement area (which is within thespare area 1702). For example, suppose that a first defective area 1704and a second defective area 1705 are judged to be defective as a resultof performing verification to see if main information is recordednormally or not. In such a case, both pieces of main informationrecorded in the first defective area 1704 and the second defective area1705 are relocated to a first replacement area 1706 and a secondreplacement area 1707 inside the spare area 1702, respectively.

[0009] However, the existing defect management processing describedabove has the problem that only main information is relocated andrecorded in a replacement area when an area is judged to be a defectivearea where main information cannot be normally recorded, causing subinformation superimposed on such main information to be unable to bereplaced and recorded.

[0010] Moreover, since only a reproduction error related to maininformation is detected in the existing technique at the time ofreproducing an area where main information and sub information arerecorded, reproduction processing keeps going on even when subinformation has become uncorrectable or subject to error correction.

[0011] The present invention has been conceived in view of the aboveproblems, and it is an object of the present invention to provide anoptical disc defect management method, an optical disc recordingapparatus and an optical disc reproduction apparatus capable ofreproducing main information and sub information in a stable manner evenwhen not only a defective area where the main information cannot benormally recorded is found, but also a defective area where the subinformation superimposed on such main information cannot be normallyrecorded is found.

DISCLOSURE OF INVENTION

[0012] The optical disc defect management method according to thepresent invention is a defect management method for an optical disc onwhich main information is recorded by forming optically-readablerecording marks, and on which sub information is recorded bysuperimposing said sub information on the main information, the opticaldisc defect management method comprising: a verification step ofverifying whether or not the main information and the sub informationhave been recorded normally, every time a predetermined amount of maininformation and sub information are recorded; and a defective areamanagement step of performing the following processes when it is judgedin the verification step that one of (i) the main information, (ii) thesub information, and (iii) the main information and the sub information,has not been recorded normally: relocating and recording, in apredetermined spare area in the optical disc, one of (i) the maininformation, (ii) the sub information, and (iii) the main informationand the sub information, regarding that a recording area where therecording has been performed is a defective area related to a recordingof one of (i) the main information, (ii) the sub information, and (iii)the main information and the sub information; and registering, into apredetermined defect management area in the optical disc, informationthat associates the defective area with a replacement area inside thespare area to which said defective area has been relocated.

[0013] Furthermore, the optical disc recording apparatus according tothe present invention is an optical disc recording apparatus forrecording, on an optical disc, main information by formingoptically-readable recording marks and recording sub information bysuperimposing said sub information on the main information, the opticaldisc recording apparatus comprising: a verification unit operable toverify whether or not the main information and the sub information havebeen recorded normally, every time a predetermined amount of maininformation and sub information are recorded; and a defective areamanagement unit operable to perform as follows when it is judged by theverification unit that one of (i) the main information, (ii) the subinformation, and (iii) the main information and the sub information, hasnot been recorded normally: relocate and record, in a predeterminedspare area in the optical disc, one of (i) the main information, (ii)the sub information, and (iii) the main information and the subinformation, regarding that a recording area where the recording hasbeen performed is a defective area related to a recording of one of (i)the main information, (ii) the sub information, and (iii) the maininformation and the sub information; and register, into a predetermineddefect management area in the optical disc, information that associatesthe defective area with a replacement area inside the spare area towhich said defective area has been relocated.

[0014] Moreover, the optical disc reproduction apparatus according tothe present invention is an optical disc reproduction apparatus forreading out main information and sub information by readingoptically-readable recording marks from an optical disc, said subinformation having been recorded by superimposing said sub informationon the main information, the optical disc reproduction apparatus,comprising: a replacement area reproduction unit operable to reproduceone of (i) the main information, (ii) the sub information, and (iii) themain information and the sub information from a replacement area where adefective area is replaced and recorded, when an area from which themain information and the sub information are to be reproduced is saiddefective area related to a recording of one of (i) the maininformation, (ii) the sub information, and (iii) the main informationand the sub information; and a reproduction error judgment unit operableto judge that there is a reproduction error in the main information andthe sub information, while the area where said main information and saidsub information are recorded is being reproduced.

[0015] In addition to the above, it is also possible to embody thepresent invention as an optical disc reproduction method that includes,as its steps, each of the constituent elements included in the opticaldisc reproduction apparatus, as well as a program for causing theoptical disc recording apparatus to execute the steps of the opticaldisc defect management method and for causing the optical discreproduction apparatus to execute the steps of the optical discreproduction method. Also, such program can be distributed on arecording medium such as CD-ROM and via a transmission medium such as acommunication network. Furthermore, it is also possible to embody thepresent invention as an optical disc on which information is recorded byuse of the optical disc defect management method.

BRIEF DESCRIPTION OF DRAWINGS

[0016]FIG. 1 is an external view showing a surface of an existingoptical disc.

[0017]FIG. 2 is a timing chart showing major signals in an optical discrecording apparatus that records sub information by superimposing it onmain information.

[0018]FIG. 3 is a conceptual diagram showing an existing linearreplacement processing.

[0019]FIG. 4 is a block diagram showing a configuration of a preferredembodiment of an optical disc recording apparatus according to thepresent invention.

[0020]FIG. 5 is a data structure diagram showing an optical disc to berecorded by the optical disc recording apparatus.

[0021]FIG. 6 is a block diagram showing a detailed configuration of arecording unit of the optical disc recording apparatus.

[0022]FIG. 7 is a timing chart showing major signals in the recordingunit.

[0023]FIG. 8 is a block diagram showing a detailed configuration of aphase modulator of the recording unit.

[0024]FIG. 9 is a block diagram showing a detailed configuration of averification/reproduction unit of the optical disc recording apparatus.

[0025]FIG. 10 is a timing chart showing major signals in theverification/reproduction unit.

[0026]FIG. 11 is a block diagram showing a configuration of a clockextractor of the verification/reproduction unit.

[0027]FIG. 12 is a block diagram showing a configuration of areproduction signal processing circuit of the verification/reproductionunit.

[0028]FIG. 13 is a block diagram showing a configuration of a subinformation detector of the verification/reproduction unit.

[0029]FIG. 14 is an explanation diagram showing an operation of athreshold value judgment unit of the sub information detector.

[0030]FIG. 15 is a flowchart showing a flow of characteristic processesperformed by the optical disc recording apparatus.

[0031]FIG. 16 is a flowchart showing a flow of a verification processperformed by the optical disc recording apparatus.

[0032]FIG. 17 is a flowchart showing another processing method of theverification process performed by the optical disc recording apparatus.

[0033]FIG. 18 is a conceptual diagram showing a sub informationverification process in the verification process.

[0034]FIG. 19 is an explanation diagram showing a case-by-caserelocation process to be performed depending on a reason why an area isjudged to be defective.

[0035]FIG. 20 is a conceptual diagram showing linear replacementalgorithm in Method A used in a defect management process performed bythe optical disc recording apparatus.

[0036]FIG. 21 is a flowchart showing a procedure of a linear replacementprocess in the defect management process performed by the optical discrecording apparatus.

[0037]FIG. 22 is a conceptual diagram showing linear replacementalgorithm in Method B used in the defect management process performed bythe optical disc recording apparatus.

[0038]FIG. 23 is an external view showing a surface of an optical discon which sub information is recorded using another superimpositionmethod.

[0039]FIG. 24 is a block diagram showing a configuration of a preferredembodiment of an optical disc reproduction apparatus according to thepresent invention.

[0040]FIG. 25 is a flowchart showing a flow of a characteristicprocessing of the optical disc reproduction apparatus.

[0041]FIG. 26 is a flowchart showing a flow of a sector numberconversion process performed by the optical disc reproduction apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

[0042] The following gives a detailed explanation of the preferredembodiment of the present invention with reference to the drawings.

[0043] (Optical Disc Recording Apparatus)

[0044]FIG. 4 is a block diagram showing the configuration of anembodiment of the optical disc recording apparatus according to thepresent invention. As shown in FIG. 4, an optical disc recordingapparatus 1 is used being connected to or incorporated into an apparatus3 such as a personal computer, and is comprised of an interface 11, arecording unit 12, a verification/reproduction unit 13, and a systemcontrol unit 14.

[0045]FIG. 5 is a data structure diagram showing an optical disc to berecorded by the optical disc recording apparatus 1. In the presentembodiment, an explanation is given using a data structure of a DVD-RAM.An optical disc 200 has a sector structure in which a certain number ofdata items, is included for recording main information. Moreover, theoptical disc 200 is made up of ECC blocks 201, each of which includes 16sectors in an integrated form, for the purpose of correcting an error inreadout information. One sector 202 in an ECC block contains 26 frames205 made up of synchronization areas 203 and data areas 204 in whichmain information is recorded.

[0046] A synchronization area 203 is intended for generating a timingsignal for demodulating a subsequent data area 204. With reference tosuch timing signal, a data area 204 is demodulated every 16 channel bitsso as to obtain main information. An address ID 206 for identifying asector 202 is placed at the top of a data area 204 in the top frame, andsuch address ID 206 is used at the time of reproduction to find a sector202 to be read out.

[0047] In FIG. 5, pieces of sub information are superimposed onrecording marks in the data areas 204 included in frames except for thetop frame of the sector 202 (the frame that includes the address ID 206)and the last frame (the next previous frame of the frame including theaddress ID 206), and 1-bit sub information is superimposed on aplurality of frames 205 (three frames in FIG. 5). For example, subinformation sd[i]b4 is superimposed on recording marks that make up dataareas 204 of the frames [10]˜[12]. As a result, 8-bit sub information isrecorded per sector, and 16-byte sub information is recorded per ECCblock.

[0048]FIG. 6 is a block diagram showing a detailed configuration of therecording unit 12 of the optical disc recording apparatus 1, and FIG. 7is a timing chart showing major signals used when recording maininformation and sub information. The recording unit 12 is intended forrecording main information by forming optically-readable recording marksof an optical disc and for recording, at the same time, sub informationby displacing the edges of such recording marks by a constant minuteamount. As shown in FIG. 6, the recording unit 12 is comprised of atiming generator 301, a modulator 302, a random number generator 303, arandom number sequence converter 304, a PE (Phase Encoding) modulator305, a phase modulator 306, a recording channel 307, and a recordinghead 308.

[0049] The timing generator 301 outputs, to the modulator 302 and therandom number generator 303, a synchronization signal A3 as shown inFIG. 7 for indicating timing at which synchronization patterns(synchronization areas) should be inserted into recorded data, whenreceiving a notification from the system control unit 14 instructingthat the recording of main information and sub information should bestarted. Furthermore, based on such synchronization signal A3 and aclock signal from a clock generator not illustrated in the diagram, thetiming generator 301 outputs a byte clock (which is a 16th of thefrequency of the clock signal) synchronized with each byte of therecorded data, and outputs, at the same time, a PE signal A6 to the PEmodulator 305 that enables H intervals and L intervals to be half andhalf in each byte, as shown in FIG. 7. Further, in order to record maininformation and sub information as shown in FIG. 5, the timing generator301 outputs, to the phase modulator 306, a phase modulation enablesignal A4, as shown in FIG. 7, indicating an area where sub informationshould be recorded (the data area of a frame which does not include theID area).

[0050] The modulator 302 inserts a synchronization pattern (asynchronization area) into the input recorded data (main information) onthe basis of the synchronization signal A3 from the timing generator301, and at the same time, generates a channel signal A2 by performingNRZI conversion on such main information to be recorded after convertingit into a corresponding 16-bit-long channel code shown in FIG. 7 on an8-bit code (byte) basis, and outputs such channel signal A2 to the phasemodulator 306.

[0051] The random number generator 303 pre-sets the initial value of arandom number at the timing indicated by the synchronization signal A3from the timing generator 301, and generates 1 bit of a pseudo randomnumber sequence A5 at the timing indicated by the byte clock as shown inFIG. 7, and outputs it to the random number sequence converter 304.

[0052] The random number sequence converter 304 performs an operationthat gives a correlation between the pseudo random number sequence A5from the random number generator 303 and each bit of sub information tobe recorded. In the present embodiment, the random number sequenceconverter 304 is configured to carry out exclusive ORs, and performsinversion/non-inversion of the pseudo random number sequence A5depending on each bit of sub information to be recorded. The resultingrandom number sequence (sub information correlation random numbersequence) is then outputted to the PE modulator 305. Sub information tobe recorded is superimposed on 24 frames except for the top and the lasttwo frames in each sector, and a bit of sub information is updated everythree frames.

[0053] On the basis of the PE signal A6 from the timing generator 301,the PE modulator 305 generates a PE modulated random number sequence (PEmodulated signal) A7 as shown in FIG. 7 by performing PE modulation onthe sub information correlation sequence outputted by the random numbersequence converter 304, and outputs such PE modulated random numbersequence A7 to the phase modulator 306. Subsequently, as the PEmodulated random number sequence A7, the PE signal A6 is directlyoutputted when the sequence (sub information correlation sequence) onwhich sub information is superimposed is 0 (rises down every 16-bitchannels), whereas the PE signal A6 is outputted in an inverted formwhen the sequence (sub information correlation sequence) on which subinformation is superimposed is 1 (rises up every 16-bit channels).Accordingly, it is possible to obtain such a signal as enables thenumber of 0 and 1 intervals to be approximately the same even in thecase where there is a sequence of the same random number sequences.

[0054] The phase modulator 306 performs phase modulation for delaying oradvancing the edges (when the phase modulation enable signal is “H”) ofonly data areas in frames, as shown in FIG. 5, in which sub informationis to be recorded, out of the channel signal A2 from the modulator 302,whereas it outputs, to the recording channel 307, the channel signal A2without performing phase modulation on the other edges (when the phasemodulation enable signal is “L”).

[0055]FIG. 8 is a block diagram showing a detailed configuration of thephase modulator 306. The phase modulator 306 is made up of delayers 402,403 and 404 for delaying a signal only for said minute period of timeand a selector 401 that accepts three inputs and generates one output.The selector 401 outputs a signal S2 resulted by delaying the channelsignal A2 inputted by the modulator 302 through the single delayer 402when the phase modulation enable signal A4 inputted as a control signalis “0”, outputs the channel signal A2 inputted by the modulator 302 asit is as a signal S1 when the phase modulation enable signal A4 is 1 andthe PE modulated random number sequence A7 is 1, and outputs a signal S3resulted by delaying the channel signal A2 inputted by the modulator 302through two delayers 403 and 404 when the phase modulation enable signalA4 is 1 and the PE modulated random number sequence A7 is 0.

[0056] As a result, the phases of recording mark edges that are recordedon (i) ECC blocks on which no sub information is superimposed, (ii)important frames which store ID and the like, and (iii) synchronizationareas of frames, are not changed, and the phases of recording mark edgesof data areas on which sub information is superimposed are advanced bythe above-mentioned minute period of time when the PE modulated randomnumber sequence A7 is 1, whereas they are to be delayed when the PEmodulated random number sequence A7 is 0.

[0057] The recording channel 307 generates a control signal for changingthe recording powers of a laser that is outputted to an optical disc 309in synchronization with 1/0 in the modulated channel signal A8 from thephase modulator 306, and outputs it to the recording head 308.

[0058] The recording head 308 forms, on the optical disc 309,optically-readable modulated recording marks A9 as shown in FIG. 7 byincreasing/decreasing the powers of the laser, based on the controlsignal from the recording channel 307.

[0059]FIG. 9 is a block diagram showing a detailed configuration of theverification/reproduction unit 13 of the optical disc recordingapparatus 1, and FIG. 10 is a timing chart showing major signals usedwhen verification and reproduction is carried out on recorded maininformation and sub information. The verification/reproduction unit 13is intended for reproducing main information which has been recorded bythe recording unit 12 by forming optically-readable recording marks aswell as sub information which has been recorded by the recording unit 12by displacing the edges of the recording marks by a constant minuteamount, and is comprised of a reproduction head 602, a reproductionchannel 603, a clock extractor 604, a reproduction signal processingcircuit 605, a random number generator 606, a PE modulator 607, and asub information detector 608.

[0060] The reproduction head 602 generates an analog readout signal byconverging optical beams so as to radiate them over the recording markson the rotating optical disc 200 and by amplifying reflected beamsreceived by a photodiode, and outputs such analog readout signal to thereproduction channel 603. The reproduction channel 603 converts theanalog readout signal from the reproduction head 602 into a digitalreadout signal B2 as shown in FIG. 10 by performing waveformequalization and sharpening on such analog readout signal, and outputsthe resulting digital readout signal to the clock extractor 604 and thereproduction signal processing circuit 605.

[0061] Based on such digital readout signal B2 from the reproductionchannel 603, the clock extractor 604 outputs a channel clock B3synchronized with channel bits, as well as a byte clock synchronizedwith each recorded data (on a byte-byte-byte basis) in the digitalreadout signal B2, and outputs them to the reproduction signalprocessing circuit 605, the random number generator 606, and the subinformation detector 608. At the same time, the clock extractor 604detects a phase error in the readout signal with reference to thechannel clock B3, and generates a phase advance error signal B5 when aphase advance is detected, whereas it generates a phase delay errorsignal B6 when a phase delay is detected, so as to output the generatedsignal to the sub information detector 608.

[0062]FIG. 11 is a block diagram showing a detailed configuration of theclock extractor 604. The clock extractor 604 is comprised of a PLLcircuit made up of a phase comparator 701, a charge pump 702 and a VCO(Voltage Controlled Oscillator) 703, and of a 16 frequency divider 704.

[0063] The phase comparator 701 calculates, from the channel clock B3feed-backed and inputted from the VCO 703 and the digital readout signalB2 from the reproduction channel 603, a phase error between a leadingedge/trailing edge in such digital readout signal B2 and a leading edgein the channel clock B3 which is closest to such edge, and outputs theresult of the calculation as the phase advance error signal B5 or thephase delay error signal B6 to the charge pump 702.

[0064] The charge pump 702 controls output voltage according to theinput phase advance error signal B5 and phase delay error signal B6. Inother words, output voltage is decreased in order to make the frequencyof the channel clock B3 lower when the phase advance error signal B5 isinputted, whereas output voltage is increased in order to make thefrequency of the channel clock B3 higher when the phase delay errorsignal B6 is inputted. The VCO 703 is a voltage controlled oscillatorthat generates the channel clock B3 at a frequency corresponding tooutput voltage from the charge pump 702.

[0065] The 16 frequency divider 704, which is a counter that divides thefrequency of the channel clock B3 from the VCO 703 into {fraction(1/16)}, is reset by a synchronization signal B4 from the reproductionsignal processing circuit 605. Subsequently, the 16 frequency divider704 generates a PE signal B9 and a byte clock synchronized with eachrecorded data (on a byte-by-byte basis) in the digital readout signalB2, with reference to each synchronization area.

[0066] The reproduction signal processing circuit 605 is a circuit fordetecting a synchronization area from the digital readout signal B2inputted by the reproduction channel 603 and demodulating the readoutsignal with reference to the synchronization area.

[0067]FIG. 12 is a block diagram showing a detailed configuration of thereproduction signal processing circuit 605. The reproduction signalprocessing circuit 605 is comprised of a synchronization signal detector802, a demodulator 801, and a gate signal generator 803.

[0068] The synchronization signal detector 802 generates asynchronization area (synchronization pattern) included in the digitalreadout signal B2, and generates the synchronization signal B4 so as tooutput it to the clock extractor 604 and the random number generator606.

[0069] The demodulator 801, which is a demodulation circuit paired withthe modulator 302 of the recording unit 12, samples the digital readoutsignal B2 inputted by the reproduction channel 603 in synchronizationwith the channel clock B3 from the clock extractor 604, and converts itinto 8-bit recorded data corresponding to a 16-bit channel code insynchronization with the byte clock inputted by the clock extractor 604,and outputs it as main information.

[0070] The gate signal generator 803 outputs, to the sub informationdetector 608, a signal (sub information detection enable signal) B7indicating the data area in frames (except for the top and the lastframes in each sector) on which sub information is recorded, withreference to the synchronization signal B4.

[0071] The random number generator 606, which has the same functionalityas that of the random number generator 303 of the recording unit 12,presets the initial value at the timing indicated by the synchronizationsignal B4 from the reproduction signal processing circuit 605, andgenerates a pseudo random number sequence B8 at the timing indicated bythe byte clock from the clock extractor 604.

[0072] The PE modulator 607, which has the same functionality as that ofthe PE modulator 305 of the recording unit 12, performs PE modulation onthe pseudo random number sequence B8 outputted from the random numbergenerator according to the PE signal B9 from the clock extractor 604,and outputs the resultant to the sub information detector 608. The subinformation detector 608 is a circuit for detecting correlation betweenthe phase advance error signal B5 and the phase delay error signal B6outputted from the clock extractor 604 and the PE modulated randomnumber sequence (PE modulated signal) from the PE modulator.

[0073]FIG. 13 is a block diagram showing a detailed configuration of thesub information detector 608. The sub information detector 608 iscomprised of a correlation detector 901, an UP/DOWN counter 902, athreshold judgment unit 903, and a sub information update timinggenerator 904.

[0074] The correlation detector 901 outputs, to the UP/DOWN counter 902,+1 when the PE modulated random number sequence B10 outputted by the PEmodulator 607 is 1 and the phase delay error signal B5 is “H”, or whenthe PE modulated random number sequence B10 is 0 and the phase delayerror signal B6 is “H”. Meanwhile, the correlation detector 901 outputs,to the UP/DOWN counter 902, −1 when the PE modulated random numbersequence B10 is 1 and the phase delay error signal B6 is “H”, or whenthe PE modulated random number sequence B10 is 0 and the phase advanceerror signal B5 is “H”.

[0075] The UP/DOWN counter 902 adds an output value (+1 or −1) from thecorrelation detector 901 when the sub information detection enablesignal B7 outputted by the reproduction signal processing circuit 605 is“H” so as to hold the addition result in its internal register, andoutputs such addition result to the threshold judgment unit 903.Meanwhile, when the sub information detection enable signal B7 is “L”,the UP/DOWN counter 902 does not perform any additions, and holds thevalue held in the internal register (does not update the value held inthe internal register). Furthermore, the UP/DOWN counter 902 clears theintegrated value held in its internal register (sets the value held inthe internal register to 0) when the sub information update signal isoutputted by the sub information timing generator 904.

[0076] Therefore, an UP/DOWN counter integrated value B11 increases inthe positive direction only when the PE modulated random number sequenceB10 is 1 and the phase advance error signal B5 is “H” or when the PEmodulated random number sequence B10 is 0 and the phase delay errorsignal B6 is “H”. On the contrary, the UP/DOWN counter integrated valueB11 decreases in the negative direction only when the PE modulatedrandom number sequence B10 is 1 and the phase delay error signal B6 is“H” or when the PE modulated random number sequence B10 is 0 and thephase advance error signal B5 is “H”. Meanwhile, in the case of areaswhere no sub information is superimposed, i.e. when neither of thecorrelations occurs and the phase advance error signal B5 and the phasedelay error signal B6 occur randomly, since these error signals occur atan approximately equal rate, the UP/DOWN counter integrated value B11shall be a value around 0.

[0077] The threshold judgment unit 903 includes a register for holdingthe integrated value B11 outputted by the UP/DOWN counter 902 as well asa comparator and the like for comparing the integrated value B11 itholds with the predetermined positive threshold value for detection,negative threshold value for detection, positive threshold value forverification and negative threshold value for verification. When the subinformation update signal is outputted by the sub information updatetiming generator 904, processing shall be performed as described below.

[0078]FIG. 14 is an explanation diagram showing the operation of thethreshold value judgment unit 903. The threshold value judgment unit 903outputs “1” as a sub information sequence when the integrated value B11held in the internal register is bigger than the positive thresholdvalue for detection at the point of time when the sub information updatesignal is outputted by the sub information update timing generator 904,whereas it outputs “0” as a sub information sequence when the integratedvalue B11 is smaller than the negative threshold value for detection andoutputs, at the same time, “H” as a detection flag indicating that thereexisted sub information. Meanwhile, when the integrated value B11 issmaller than the positive threshold value for detection and smaller thanthe negative threshold value for detection, the threshold value judgmentunit 903 outputs “L” as a detection flag, judging that there is nocorrelation (sub information).

[0079] Furthermore, the threshold value judgment unit 903 outputs “H” asa detection flag, judging that sub information is defective, when theintegrated value B11 held in the internal register is bigger than thepositive threshold value for detection and smaller than the positivethreshold value for verification, and when it is smaller than thenegative threshold value for detection and bigger than the negativethreshold value for verification at the point of time when the subinformation update signal is outputted by the sub information updatetiming generator 904. On the other hand, when the integrated value B11is bigger than the positive threshold value for verification and smallerthan the negative threshold value for verification, the threshold valuejudgment unit 903 outputs “L” as a detection flag, judging that there isno defect in sub information. Meanwhile, when the integrated value B11is smaller than the positive threshold value for detection and smallerthan the negative threshold value for detection, the threshold valuejudgment unit 903 outputs “L” as a detection flag, judging that there isno correlation and therefore that there is no defect in sub information.

[0080] The sub information update timing generator 904 generates timingto update sub information on the basis of the input synchronizationsignal B4. The sub information update signal in the present embodiment,which is a signal whose pulse is outputted to the frames excluding thetop and the last frames in each sector every three frames, clears thevalue held in the UP/DOWN counter 902 and updates the judgment resultobtained by the threshold value judgment unit 903.

[0081] Next, an explanation is given of the operation of the opticaldisc recording apparatus 1 with the above configuration. FIG. 15 is aflowchart showing the flow of characteristic processes performed by theoptical disc recording apparatus 1.

[0082] The optical disc recording apparatus 1 performs: the recordingprocess for recording main information and sub information in aspecified area (Step S101); the verification/reproduction process forreproducing main information to be verified and sub information to beverified from the above specified area (Step S102); the verificationprocess for verifying whether the area where the recording process hasbeen performed can be reproduced in a stable manner or not, on the basisof the reproduced main information and sub information to be verified(Steps S103 and S104); and the defect management process for conductingdefect management of the above area as a defective area when it isjudged in the verification process that such area is unable to bereproduced in a stable manner, and relocating the main information andthe sub information to an area in which recording can be performed in astable manner (Step S105).

[0083] In the recording process S101, the system control unit 14memorizes main information and sub information to be recorded that areequivalent to 16 sectors (an ECC block unit), and instructs therecording unit 12 to perform recording.

[0084] In the recording unit 12, when the timing generator 301 outputs“H” to the synchronization signal A3, the modulator 302 generates achannel signal (synchronization pattern) which constitutes thesynchronization area 501 of each frame. When the synchronization signalA3 is “L”, the modulator 302 modulates main information to be recorded(8-16 modulation for DVDs), and outputs it as a channel signal. Thetiming signal generator 301 outputs “L” to the synchronization signal A3according to the data area 502 in a frame where sub information is to berecorded, and outputs, at the same time, the phase modulation enablesignal A4 to the phase modulator 306.

[0085] The random number generator 303 initializes the random numbersequence when the synchronization signal A3 is “H”, whereas it generatesthe pseudo random number sequence A5 bit by bit in synchronization withthe byte clock when the synchronization signal A3 is “L”. The randomnumber sequence converter 304 carries out exclusive OR between suchpseudo random number sequence A5 and sub information to be recorded, andgenerates a sub information correlation sequence (it will be the same asthe pseudo random number sequence A5 when sub information to be recordedis “0”, whereas it will be the result of inverting the pseudo randomnumber sequence A5 when sub information to be recorded is “1”). Anexample shown in FIG. 7 illustrates the case where sub information to berecorded is 0 and where the sub information correlation sequence and thepseudo random number sequence A5 are the same. Moreover, the PEmodulator 305 performs PE modulation on the sub information correlationsequence (which is the same as the pseudo random number sequence A5,here) on the basis of the PE signal A6 from the timing generator 301,and obtains the PE modulated random number sequence A7.

[0086] The phase modulator 306 outputs the channel signal A2 as it is asthe modulated channel signal A8 when the phase modulation enable signalA4 is “L”, whereas it advances or delays the phase of an edge of thechannel signal A2 depending on the value of the PE modulated randomnumber sequence A7, when the phase modulation enable signal A4 is “H”.Here, processing is performed for advancing the edge of the channelsignal by At when the PE modulated random number sequence A7 is “1”,whereas processing is performed for delaying the edge of the channelsignal by At when the PE modulated random number sequence A7 is “0”.Modulated recording marks A9 can be formed on an optical disc bycontrolling the laser by use of the modulated channel signal A8generated in the above manner.

[0087] As described above, the recording unit 12 not only records maininformation, but also superimposes and records sub information (in thepresent embodiment, 128 bits per ECC block) by performing phasemodulation on the recording mark edges of the main information by aconstant minute amount.

[0088] Next, in the verification/reproduction process S102, when therecording processing ends, the system control unit 14 instructs theverification/reproduction unit 13 to perform verification/reproductionof recorded main information and sub information that are equivalent to16 sectors (an ECC block unit).

[0089] In the verification/reproduction unit 13, when the digitalreadout signal B2 is inputted, the clock extractor 604 generates thechannel clock B3 resulted by synchronizing both of its edges with thephase of leading edges of the channel clock B3. The reproduction signalprocessing circuit 605 searches for a synchronization area in the databy sampling the digital readout signal B2 at the timing indicated bytrailing edges of the channel clock B3 and making a comparison to see ifthey match a specified synchronization pattern. On the detection of apattern that matches the synchronization pattern, the reproductionsignal processing circuit 605 outputs the synchronization signal B4 fromthe synchronization signal detector 802, and outputs the sub informationdetection enable signal B7 from the gate signal generator 803 accordingto the data area of frames (except for the top and the last frames ineach sector) in which sub information is superimposed.

[0090] When the synchronization signal B4 is outputted, the clockextractor 604 clears the internal 16 frequency divider, and outputs thebyte clock that is resulted by dividing the frequency of the channelclock B3 into {fraction (1/16)} as well as the PE signal B9. Also, whenthe synchronization signal B4 is outputted, the random number generator606 initializes the random number sequence (an initial value is set inthe internal register at the timing indicated by an initializationtiming 1), and outputs the pseudo random number sequence B8 bit by bitat the timing indicated by the byte clock (every 16 channel clocks).From such pseudo random number sequence B8 and the PE signal B9, the PEmodulator 607 generates the PE modulated random number sequence B10 inwhich the respective 8 channel clocks out of 16 channel clocks form aninterval of 1 and an interval of 0.

[0091] The clock extractor 604 detects a phase error between a leadingedge of the channel clock B3 and an each of edges of the digital readoutsignal B2, and outputs the phase advance error signal B5 when an edge ofthe digital readout signal B2 advances further than a leading edge ofthe channel clock B3, whereas it outputs the phase delay error signal B6when an edge of the digital readout signal B2 is behind a leading edgeof the channel clock B3.

[0092] The sub information detector 608 adds the phase advance errorsignal B5 and subtracts the phase delay error signal B6 during aninterval in which the PE modulated random number sequence B10 is 1, whenthe sub information detection enable signal B7 is “H”. The subinformation detector 608 adds the phase delay error signal B6 andsubtracts the phase advance error signal B5 during an interval in whichthe PE modulated random number sequence B10 is 0. In an example shown inFIG. 10, since the phase advance error signal B5 is outputted during aninterval in which the PE modulated random number sequence B10 is 1 andthe phase delay error signal B6 is outputted during an interval in whichthe PE modulated random number sequence B10 is 0, the integrated valuedetermined by the UP/DOWN counter 902 of the sub information detector608 increases.

[0093] Accordingly, at the point of time when integrations for apredetermined number of frames are finished (3 frames in the presentembodiment) (at the time when sub information update signal isoutputted), “1” is detected as sub information (a detection flag “1” isoutputted at the same time) when the integrated value determined by theUP/DOWN counter 902 is bigger than the positive threshold value fordetection, “0” is detected as sub information (a detection flag “1” isoutputted at the same time) when the integrated value is smaller thanthe negative threshold value for detection, and a detection flag “0” isoutputted when the integrated value is in between a negative correlationthreshold value and a positive correlation threshold value.

[0094] Next, in the verification process S103, a judgment is made onwhether or not main information and sub information recorded on theoptical disc can be read out in a stable manner. To put it another way,a verification is performed to see if areas in which the recordingprocess has been performed can be read out in a stable manner, on thebasis of sub information readout on an ECC block basis (128 bits) andmain information outputted by the reproduction signal processing circuit605 in the verification/reproduction processing S102.

[0095]FIG. 16 is a flowchart showing the flow of such verificationprocess. The system control unit 14 of the optical disc recordingapparatus 1 performs: the sector number verification process forverifying whether a sector number in which main information superimposedwith sub information can be read out in a stable manner or not (StepS1101); the main information verification process for verifying whetherrecorded main information can be read out in a stable manner or not(Step S1102); and the sub information verification process for verifyingwhether sub information superimposed on such main information can beread out in a stable manner or not (Step S1103). Note that FIG. 17 is aflowchart which shows the flow of another processing method of thisverification process and which shows the flow in the case where therelocation process is performed using Method B in a detection managementprocess S104 to be described later. Here, the sub informationverification process S1103 is carried out even when it is judged, in themain information verification process S1102, that main informationcannot be read out in a stable manner.

[0096] In the sector number verification process S1101, the systemcontrol unit 14 performs a verification to see if one or more sectornumbers physically embedded in the optical disc can be reliably readoutor not. In a DVD-RAM, for example, there are four areas called CAPAs atthe top of a sector in which the sector number is embedded, and athreshold value which enables at least one of these to be read out underany conditions is set and verified. When a sector number readout errorsequivalent to a value equal to or bigger than such threshold valueoccur, the defect management process shall be performed on such physicalsector as a defective area. If the verification succeeds, the maininformation verification process is then carried out for checking thereliability of reading out the main information.

[0097] In the main information verification process S1102, the systemcontrol unit 14 compares real main information recorded by the recordingoperation with the main information to be verified that is extracted atthe time of verification/reproduction, so as to determine how many bytesof errors are detected. Next, the system control unit 14 judges whetheror not the determined number of byes of error detections is over athreshold value that has been set in advance on the basis of the numberof error-correctable bytes included in an ECC block in order that maininformation can be read out in a stable manner even under a certaindegree of adverse conditions. If the result of such judgment is thatthere exist error detections over the threshold value, the defectmanagement process shall be performed on an area including such sectoras a defective area related to main information. Also, since it isimpossible to carry out an error correction when an error correction isdetected by an error correcting and detecting code within an ECC block,the defect management process shall also be performed on an areaincluding such sector as a defective area related to main information.When the verification of the main information succeeds, the subinformation verification process S1103 is then performed.

[0098] Any of the following three methods shall be used as the subinformation verification process S1103.

[0099] (Method 1)

[0100] The system control unit 14 performs a verification to see if subinformation can be read out in a stable manner or not, on the basis of averification flag outputted by the threshold value judgment unit 903 ofthe sub information detector 608. To put it another way, the systemcontrol unit 14 counts the number of bits where the verification flagwas “H” out of the whole sub information sequence (128 bits in thepresent embodiment), and judges whether such number of bits is over apredetermined threshold value or not. If the result of such judgment isthat the counted number of bits exceeds the threshed value, the defectmanagement process shall be performed as a defective area related to thesub information. Meanwhile, when the counted number of bits does noexceed the threshold value, i.e. when the sub information verificationsucceeds, the verification/reproduction process is terminated, withsector numbers, main information and sub information being regarded asreproducible in a stable manner.

[0101] (Method 2)

[0102] The system control unit 14, through the threshold value judgmentunit 903 of the sub information detector 608, determines how many bytesof errors are detected, by making a bit comparison between (i) a subinformation sequence to be verified extracted on the basis of thecorrelation value (integrated value) integrated in the UP/DOWN counter902 and the predetermined positive threshold value fordetection/negative threshold value for detection and (ii) the real subinformation recorded at the time of the recording operation.

[0103]FIG. 18 is a conceptual diagram showing this sub informationverification process. Comparison and verification is made on subinformation to be verified 1201 and sub information 1202 on a bit-by-bitbasis in order to verify if the sub information can be read out in astable manner or not by making a comparison between (i) the number ofbits out of the whole sequence (128 bits in the present embodiment)which do not match, i.e. the number of bits where errors are detected inthe sub information and (ii) a predetermined threshold value A.

[0104] The threshold value A is set to a value equal to or smaller thanthe number of correctable bits to be determined depending on parity codeincluded in sub information itself. In the present embodiment, thebreakdown of sub information to be recorded in each ECC block is assumedto be: 64-bit confidential information; a 48-bit error correcting code;and a 16-bit error correcting and detecting code. In this case, even iferrors of up to 6 bits are detected out of 128 bits, it is possible toextract sub information in a stable manner by correcting such anerror-detected bit. Because of this reason, a value serving as thethreshold value A shall be 6 or smaller in the present embodiment. Whenthe number of error-detected bits in sub information exceeds suchthreshold value A, the defect management process is conducted as adefective area related to the sub information. Similarly, when it isrecognized that an error correction has been conducted by the errorcorrecting and detecting code of sub information, the defect managementprocess shall also be performed as a defective area related to subinformation. When the verification of the main information succeeds, theverification/reproduction process is terminated, with sector numbers,main information and sub information being regarded as reproducible in astable manner.

[0105] (Method 3)

[0106] The system control unit 14 verifies if sub information can beread out in a stable manner or not by comparing, with the predeterminedthreshold value A, the number of errors detected by performing an errorcorrection by use of the parity code included in the sub informationitself. When the number of error detected bits at the time of the errorcorrection has proven to exceed such threshold value A, the defectmanagement process shall be performed as a defective area related to subinformation. When the number of error detected bits does not exceed thethreshold value, i.e. when the verification of the sub informationsucceeds, the verification/reproduction process is terminated, withsector numbers, main information and sub information being regarded asreproducible in a stable manner.

[0107] Note that although the defect management process is immediatelycarried out when an area where information is recorded has been judgedto be a defective area in any one of the sector number verificationprocess, the main information verification process and the subinformation verification process, the retry process may be carried outinstead for trying to record the same main information and subinformation again in the same area.

[0108] As described above, the defect management process S104 shall beperformed when an area where sector numbers, main information and subinformation are recorded is judged to be a defective area in the sectornumber verification process, the main information verification process,and the sub information verification process of the verification processS103. In the present embodiment, the defect management is conducted inaccordance with the linear replacement algorithm that is one of thedefect management processes intended for DVD-RAMs.

[0109] In the linear replacement algorithm, when a defective area isfound at the time of verifying the recorded information, it is relocatedto a spare area which is provided in advance within an optical disc userarea. Then, the respective top sector numbers of such defective area andits corresponding replacement area are registered and managed, as anentry pair, on a defect management list (SDL) which exists in a lead-inarea and a lead-out area of an optical disc. The above defective areaand replacement area are provided for each ECC block (16 sectors) andrelocation processing is performed on them on an ECC block basis.

[0110]FIG. 19 is an explanation diagram showing a case-by-caserelocation process to be performed depending on a reason why an area isjudged to be defective. The following explains Method A for relocating,into a replacement area, main information and sub information to berecorded in a defective area when such defective area is judged to bedefective in either the main information verification process or the subinformation verification process as shown in FIG. 16, as well as MethodB for performing relocation process depending on whether an area isjudged to be defective in the main information verification process orin the sub information verification process as shown in FIG. 17.

[0111] (Method A)

[0112]FIG. 20 is a conceptual diagram showing the linear replacementalgorithm in Method A. As shown in FIG. 20A, inside an optical disc are:a user area 1301 in which main information is stored by formingoptically-readable recording marks and in which sub information isstored by displacing their recording mark edges by a constant minuteamount; a spare area 1302 to which relocation is performed when the userarea 1301 is a defective area; and, as shown in FIG. 20B, a secondarydefect list (SDL) 1303 for managing the respective top sector numbers ofa defective area and a replacement area as an entry pair when suchdefective area is relocated to the replacement area (which is inside thespare area 1302).

[0113] Here, assume that a defective area A1304 is an area in which maininformation A and sub information A are stored and which is judged to bea defective area in the verification process carried out for the maininformation A, and that a defective area B 1305 is an area in which maininformality B and sub information B are stored and which is judged to bea defective area in the verification process carried out for the subinformation B.

[0114]FIG. 21 is a flowchart showing the procedure of the linearreplacement process according to the present embodiment. When an area isjudged to be defective in the main information verification process asin the case of the defective area A1304, for example, the system controlunit 14 searches the spare area 1302 for an available area, and obtainsthe sector number of the top sector in such available area (Step S1401).Since the relocation process is carried out on an ECC block (16 sectors)basis as described above, the system control unit 14 judges whether all16 sectors required for relocation are within the spare area 1302 ornot, starting from the top sector of the available area (Step S1402).When the result of the judgment is that a sector which is not within thespare area 1302 is included, an error termination shall be applied. Whenall the 16 sectors are within the spare area 1302, on the other hand, itmeans that an area to which relocation can be performed has beenreserved. Such reserved area shall be treated as a replacement areaA′1306 corresponding to the defective area A1304, and the obtained topsector number is treated as the top sector number of such replacementarea A′1306. The system control unit 14 adds the respective topaddresses of the defective area A1304 and the replacement area A′1306 tothe SDL 1303 as an entry (Step S1403). Finally, the system control unit14 instructs the recording unit 12 to relocate and record the maininformation A and the sub information A, which were supposed to berecorded in the defective area A1304, starting from the top sector ofthe replacement area A′1306 (Step S1404), and terminates the process.

[0115] Next, when an area is judged to be defective in the subinformation verification process as in the case of the defective areaB1305, for example, the system control unit 14 obtains an available areafrom the spare area 1302 as in the case of the defective area A1304, andtreats it as a replacement area B′1307. Then, the system control unit 14adds the respective top addresses of the defective area B1305 and thereplacement area B′1307 to the SDL 1303 as an entry. Finally, the systemcontrol unit 14 instructs the recording unit 12 to relocate and recordthe main information B and the sub information B, which are equivalentto an ECC block and which were supposed to be recorded in the defectivearea B1305, into the 16 sectors that begin with the top sector number ofthe replacement area B′1305, and terminates the process.

[0116] (Method B)

[0117]FIG. 22 is a conceptual diagram showing the linear replacementalgorithm in Method B. As shown in FIG. 22A, inside an optical disc are:a user area 1901 and a spare area 1902, and as shown in FIG. 22B, asecondary defect list (SDL) 1909 for managing information concerning thetime when defective areas are relocated to the respective replacementareas (which are inside the spare area 1902), as in the case shown inFIG. 20. In the SDL 1909, the following are managed in association withone another: a defective area list 1910 indicating the top sectornumbers of the respective defective areas; a replacement area list 1911indicating the top sector numbers of the respective replacement areas(which are inside the spare area 1902) corresponding to the abovedefective areas; a main information defect flag 1912 indicating whetheror not each of the defective areas is judged to be defective in the maininformation verification process; and a sub information defect flag 1913indicating whether or not each of the defective areas is judged to bedefective in the sub information verification process.

[0118] Here, assume that a defective area C1903 is an area in which maininformation C and sub information C are stored and which is judged to bea defective area only in the verification process carried out for themain information C, that a defective area D 1904 is an area in whichmain informality D and sub information D are stored and which is judgedto be a defective area only in the verification process carried out forthe sub information D, and that a defective area E1905 is an area inwhich main information E and sub information E are stored and which isjudged to be a defective area in the verification processes carried outfor the main information E and the sub information E.

[0119] For example, when an area is judged to be defective only in theverification process for the main information C as in the case of thedefective area C1903, the system control unit 14 obtains a replacementarea as in the case of Method A, and relocates and records only the maininformation C in a replacement area C′1906. When this is done, in theSDL 1909, the respective top sector numbers of the defective area C1903and the replacement area C′1906 are set, as well as “1” is set as themain information defect flag 1912 and “0” is set as the sub informationdefect flag 1913.

[0120] Meanwhile, when an area is judged to be defective only in theverification process for the sub information D as in the case of thedefective area D1904, the system control unit 14 obtains a replacementarea as in the case of Method A, and relocates and records only the subinformation D in a replacement area D′1907. When this is done, in theSDL 1909, the respective top sector numbers of the defective area D1904and the replacement area D′1907 are set, as well as “0” is set as to themain information defect flag 1912 and “1” is set as the sub informationdefect flag 1913. Note that dummy information may simply be recorded asmain information, when only the sub information D is relocated andrecorded in the replacement area D′1907.

[0121] Also, when an area is judged to be defective in the verificationprocesses for both the main information E and the sub information E asin the case of the defective area E1905, the system control unit 14obtains a replacement area as in the case of Method A, and relocates andrecords the main information E and the sub information E in areplacement area E′1908. When this is done, in the SDL 1909, therespective top sector numbers of the defective area E1905 and thereplacement area E′1908 are set, as well as “1” is set as the maininformation defect flag 1912 and “1” is set as the sub informationdefect flag 1913.

[0122] As described above, the same main information and sub informationare relocated and recorded again in a replacement area, when such maininformation and sub information are judged, in the respectiveverification processes, that they cannot be read out in a stable manner.Accordingly, it is possible to circumvent the phenomenon in which, whena decryption key for an encrypted content is recorded as subinformation, for example, the encrypted content which is maininformation is recorded but the decryption key for decrypting suchencrypted content fails to be recorded.

[0123] Moreover, it is possible to record sub information in the samearea as the one where main information is recorded in a stable manner,even in the case where copying management information for managing thetransfer or copying of contents between recording media, is recorded assub information. Accordingly, it is possible to update, in a stablemanner, copying management information indicating the number of timesfor which transfer is allowed between recording media and the number oftimes for which copying is allowed between recording media, and thelike.

[0124] Generally, once-recorded information shall not be deleted evenwhen an area storing such information is judged to be a defective area,but information in a once-recorded defective area may be deleted in thecase where a decryption key for content encryption and confidentialinformation such as copying management information are recorded as subinformation.

[0125] Also, when video information is recorded as main information andits corresponding audio information is recorded as sub information, itis possible to prevent information from becoming audio-only informationor video-only information.

[0126] Furthermore, when a defective area is judged in the verificationprocess that only its main information cannot be read out in a stablemanner and therefore only such main information is relocated andrecorded with sub information being left in such defective area, itbecomes possible to make an efficient use of a limited space of therecording area on an optical disc, since the sub information, which hasbeen recorded in a recording method different from a recording methodused for the main information, can be recorded in the maininformation-related defective area, in which information cannot berecorded by an existing technique.

[0127] Accordingly, even when there exists a defective area related tothe recording of the main information or the sub information, or boththe main information and the sub information due to dust, scar, fingerprint and other factors on an optical disc, since the main informationor the sub information, or both the main information and the subinformation is/are relocated and recorded in a replacement area, it ispossible to create an optical disc from which main information and subinformation can be read out in a stable manner.

[0128] Note that although the optical disc defect management method hasbeen explained in the present embodiment by taking an example case wheresub information is recorded by means of phase modulation for changingthe position of standard edges of recording marks that constitute maininformation by a minute amount in the moving direction of track, thepresent invention is not limited to this. As shown in FIG. 23, forexample, the present invention is also applicable to the case where subinformation is recorded by means of phase modulation for changing thestandard position of recording marks 210 that constitute maininformation on the optical disc 200 by a minute amount in the directionintersecting the moving direction of track. Furthermore, the presentinvention is also applicable to the case where a modulation rule and thelike is employed in which sub information is recorded by triggering biterrors by acting against the rules that are determined depending on thetype of an optical disc.

[0129] (Optical Disc Reproduction Apparatus)

[0130]FIG. 24 is an explanation diagram showing the configuration of anembodiment of the optical disc reproduction apparatus according to thepresent invention. An optical disc reproduction apparatus 2 is anapparatus for reproducing main information and sub information from anoptical disc which have been recorded by the optical disc recordingapparatus 1. As shown in FIG. 24, this optical disc reproductionapparatus 2 is used being connected to or incorporated into an apparatus3 such as a personal computer, and is comprised of an interface 21, areproduction unit 22, and a system control unit 23. Note that anexplanation of the reproduction unit 22 is omitted here since it has anequivalent functionality/configuration as that of theverification/reproduction unit 13 of the optical disc recordingapparatus 1.

[0131]FIG. 25 is a flowchart showing the flow of characteristicprocesses of the optical disc reproduction apparatus 2. The optical discreproduction apparatus 2 performs the following processes: the sectornumber conversion process for converting a logical sector number LSNspecified by the system control unit 23 into a physical sector numberPSN included in an optical disc itself (Step S1501); the reproductionprocess for reproducing main information and sub information from thephysical sector number converted in the sector number conversion process(Step S1502); and the error correction process for correcting errors inthe main information and the sub information (Step S1503).

[0132] In the sector number conversion process S1501, a process forconverting a logical sector number that is specified according to areproduction instruction from the system control unit 23 into thephysical sector number of the corresponding physical sector of anoptical disc. FIG. 26 is a flowchart showing the flow of the sectornumber conversion process. Here, the flow of converting a logical sectornumber specified by the system control unit 23 into a physical sectornumber is illustrated, for it is usual that a logical sector specifiedby the system control unit 23 and a physical sector do not correspond toeach other from the standpoint of continuity, when such physical sectorof the optical disc is a defective sector and when, therefore, it isrelocated to a spare area by the optical disc recording apparatus 1.Conversion between a logical sector number and a physical sector numberis performed with reference to the secondary defect list (in the presentembodiment, the secondary defect list SDL for the linear defectreplacement process) which is recorded inside the optical disc.

[0133] First, a temporary physical sector number TMP_PSN is determinedby adding a fixed number of offsets to the logical sector number LSNrequested by the system control unit 23 (Step S1601). The system controlunit 23 judges whether or not such temporary physical sector numberTMP_PSN is registered in the secondary defect list SDL (Step S1602).When the result of the judgment is that the temporary physical sectornumber TMP_PSN is not registered in the secondary defect list SDL(meaning that it is not a defective block), this temporary physicalsector number TMP_PSN is outputted as a physical sector number PSNcorresponding to the requested logical sector number LSN (Step S1603).

[0134] When such temporary physical sector number TMP_PSN is registeredin the secondary defect list SDL (meaning that it is a defective block),on the other hand, the sector number of a replacement area registered asan SDL entry is outputted as the physical sector number PSNcorresponding to the requested logical sector number LSN (Step S1604).Then, the relocation process is performed using Method B that wasdescribed when explaining the optical disc recording apparatus 1, andwhen there is the SDL 1909 as shown in FIG. 22B, for example, the systemcontrol unit 23 judges whether only the main information is relocatedand recorded in the replacement area, whether only the sub informationis relocated and recorded in the replacement area, or whether both themain information and sub information are relocated and recorded in thereplacement area, on the basis of the main information defect flag 1912and the sub information defect flag 1913 recorded in the SDL 1909.

[0135] When only the main information is relocated and recorded in thereplacement area, the sector number of the replacement area registeredin the SDL 1909 is outputted as the physical sector number PSNcorresponding to the requested logical sector number LSN regarding themain information, and the temporary physical sector number TMP_PSN isoutputted as the physical sector number PSN corresponding to therequested logical sector number LSN regarding the sub information.Meanwhile, when only the sub information is relocated and recorded inthe replacement area, the sector number of the replacement arearegistered in the SDL 1909 is outputted as the physical sector numberPSN corresponding to the requested logical sector number LSN regardingthe sub information, and the temporary physical sector number TMP_PSN isoutputted as the physical sector number PSN corresponding to therequested logical sector number LSN regarding the main information.

[0136] Next, in the reproduction process S1502, the system control unit23 instructs the reproduction unit 22 to reproduce the main informationand the sub information recorded on the optical disc based on thephysical sector number PSN determined in the sector number conversionprocess S1501. The reproduction unit 22 outputs, to the system controlunit 23, the main information and the sub information obtained byreproducing the optical disc. Note that the reproduction unit 22performs reproduction in a manner which is equivalent to that of theverification/reproduction unit 13 of the optical disc recordingapparatus 1.

[0137] Next, in the error correction process S1503, the system controlunit 23 performs error correction by use of correcting codes included inthe main information and the sub information that have been outputted bythe reproduction unit 22 (There is a case where sub informationpossesses no correcting codes. In the present embodiment, 128-bit subinformation is superimposed on an ECC block basis, the breakdown ofwhich is 64-bit confidential information, a 48-bit error correctingcode, and a 16-bit error correcting and detecting code). Then, thesystem control unit 23 judges whether the main information and the subinformation are error-correctable or not (Steps S1504 and S1505). In thecase where either the main information or the sub information becomesuncorrectable during error correction, or where error corrections aredetected by the respective error correcting and detecting codes, areproduction error is applied. Meanwhile, a normal termination shall beapplied when the main information and the sub information areerror-correctable and have been readout completely.

[0138] Next, an explanation is given of the case where the relocationprocess is performed using Method B that was described when explainingthe optical disc recording apparatus 1, and the user area 1901 thatincludes the defective area C1903, the defective area D1904, and thedefective area E1905 as shown in FIG. 22A is reproduced, for example, bythe optical disc reproduction apparatus 2.

[0139] In this case, regarding the defective area C1903, since only themain information is relocated and recorded in the replacement areaC′1906, the main information C is reproduced from the replacement areaC′1906 and the sub information C is reproduced normally from thedefective area C1903. Regarding the defective area D1904, since only thesub information is relocated and recorded in the replacement areaD′1907, the main information D is reproduced normally from the defectivearea D1904 and the sub information D is reproduced from the replacementarea D′1907. Regarding the defective area E1905, since the maininformation and sub information are relocated and recorded in thereplacement area E′1908, the main information E and the sub informationE are reproduced from the replacement area E′1908. In this manner, maininformation and sub information are reproduced.

[0140] As described above, even when there exists a defective arearelated to the recording of the main information or the sub information,or both the main information and the sub information, and where the maininformation or the sub information, or both the main information and thesub information i s/are recorded in a replacement area of such defectivearea, it is possible to reproduce the main information and the subinformation from the replacement area in a stable manner, by checkingthe physical sector of such replacement area with reference to thesecondary defect list inside an optical disc.

[0141] Moreover, even when a reproduction error of main information or areproduction error of sub information is detected due to dust, scar,finger print and other factors on an optical disc, it is possible toprevent only the main information from being reproduced or only the subinformation from being reproduced, by judging that it is a reproductionerror concerning the reproduction of both the main information and thesub information.

[0142] Note that, in the present embodiment, a reproduction error ofeither main information or sub information is judged to be areproduction error concerning the reproduction of both the maininformation and the sub information as described above, but the presentinvention is not limited to this. For example, a reproduction error ofmain information may be judged to be a reproduction error concerning thereproduction of both the main information and the sub information. Theformer is applicable to the case where the reproduction of subinformation has a serious influence on the reproduction of maininformation such as in the case where a content decryption key andcopying management information (the number of content transfer times,the number of content copying times etc.) are recorded as subinformation. The latter, on the other hand, is applicable to the casewhere the reproduction of sub information does not have any influenceson the reproduction of main information such as in the case where videodata is recorded as main information and audio data is recorded as subinformation.

[0143] Also, although relocation is conducted to a spare area when thereis a defective area in the user area in the present embodiment,relocation may be conducted also to another spare area when there is adefective area in the spare area.

[0144] As is obvious from the above explanations, the optical discdefect management method according to the present invention is a defectmanagement method for an optical disc on which main information isrecorded by forming optically-readable recording marks, and on which subinformation is recorded by superimposing said sub information on themain information, the optical disc defect management method comprising:a verification step of verifying whether or not the main information andthe sub information have been recorded normally, every time apredetermined amount of main information and sub information arerecorded; and a defective area management step of performing thefollowing processes when it is judged in the verification step that oneof (i) the main information, (ii) the sub information, and (iii) themain information and the sub information, has not been recordednormally: relocating and recording, in a predetermined spare area in theoptical disc, one of (i) the main information, (ii) the sub information,and (iii) the main information and the sub information, regarding that arecording area where the recording has been performed is a defectivearea related to a recording of one of (i) the main information, (ii) thesub information, and (iii) the main information and the sub information;and registering, into a predetermined defect management area in theoptical disc, information that associates the defective area with areplacement area inside the spare area to which said defective area hasbeen relocated.

[0145] Accordingly, even when there exists a defective area related tothe recording of the main information or the sub information, or boththe main information and the sub information due to dust, scar, fingerprint and other factors on an optical disc, since the main informationor the sub information, or both the main information and the subinformation is/are relocated and recorded in a replacement area, it ispossible to create an optical disc from which main information and subinformation can be read out in a stable manner.

[0146] What is more, in a defective area related to the recording ofmain information, since only the main information can be relocated andrecorded with sub information being left in such defective area, it ispossible to record sub information, which is recorded in a recordingmethod different from a recording method used for the main information,to the defective area related to the main information in whichinformation cannot be recorded by an existing technique. This allows anefficient use of a limited space of the recording area on an opticaldisc.

[0147] Also, the optical disc reproduction apparatus according to thepresent invention is an optical disc reproduction apparatus for readingout main information and sub information by reading optically-readablerecording marks from an optical disc, said sub information having beenrecorded by superimposing said sub information on the main information,the optical disc reproduction apparatus, comprising: a replacement areareproduction unit operable to reproduce one of (i) the main information,(ii) the sub information, and (iii) the main information and the subinformation from a replacement area where a defective area is replacedand recorded, when an area from which the main information and the subinformation are to be reproduced is said defective area related to arecording of one of (i) the main information, (ii) the sub information,and (iii) the main information and the sub information; and areproduction error judgment unit operable to judge that there is areproduction error in the main information and the sub information,while the area where said main information and said sub information arerecorded is being reproduced.

[0148] Accordingly, even when there is a defective area related to therecording of the main information or the sub information, or both themain information and the sub information, and the main information orthe sub information, or both the main information and the subinformation is/are recorded in a replacement area corresponding to suchdefective area, it is possible to reproduce the main information and thesub information from this replacement area in a stable manner.

[0149] Moreover, even when a reproduction error of main information or areproduction error of sub information is detected due to dust, scar,finger print and other factors on an optical disc, it is possible toprevent only the main information from being reproduced or only the subinformation from being reproduced, by judging that it is a reproductionerror concerning the reproduction of both the main information and thesub information.

[0150] Since main information and sub information can be reproduced in astable manner even in the case where a content decryption key isrecorded as sub information, for example, it is possible to circumventsuch a problem as one in which an encrypted content is reproduced as itis because of the reason that the sub information is irreproducible andtherefore that the content of the main information cannot be decrypted.

[0151] Industrial Applicability

[0152] As described above, the optical disc defect management method andthe optical disc reproduction method according to the present inventionare suited to be employed by an optical disc recording apparatus forrecording main information and recording sub information bysuperimposing it on such main information on an optical disc includingDVD as well as by an optical disc reproduction apparatus for reproducingsuch main information and sub information from the optical disc.

1. A defect management method for an optical disc on which maininformation is recorded by forming optically-readable recording marks,and on which sub information is recorded by superimposing said subinformation on the main information, the optical disc defect managementmethod comprising: a verification step of verifying whether or not themain information and the sub information have been recorded normally,every time a predetermined amount of main information and subinformation are recorded; and a defective area management step ofperforming the following processes when it is judged in the verificationstep that one of (i) the main information, (ii) the sub information, and(iii) the main information and the sub information, has not beenrecorded normally: relocating and recording, in a predetermined sparearea in the optical disc, one of (i) the main information, (ii) the subinformation, and (iii) the main information and the sub information,regarding that a recording area where the recording has been performedis a defective area related to a recording of one of (i) the maininformation, (ii) the sub information, and (iii) the main informationand the sub information; and registering, into a predetermined defectmanagement area in the optical disc, information that associates thedefective area with a replacement area inside the spare area to whichsaid defective area has been relocated.
 2. The optical disc defectmanagement method according to claim 1, wherein the verification stepincludes: a main information verification step of judging whether themain information has been recorded normally or not, and regarding therecording area as the defective area related to the recording of themain information, when it is judged that the main information has notbeen recorded normally; and a sub information verification step ofjudging whether the sub information has been recorded normally or not,and regarding the recording area as the defective area related to therecording of the sub information, when it is judged that the subinformation has not been recorded normally.
 3. The optical disc defectmanagement method according to claim 2, wherein in the main informationverification step, it is judged, based on the recorded main informationand main information to be verified that is obtained by reproducing therecording area in which said main information is recorded, whether saidmain information to be verified is normally recorded or not.
 4. Theoptical disc defect management method according to claim 2, wherein thesub information is recorded according to a sub information correlationsequence that is generated based on a predetermined pseudo random numbersequence and said sub information, and in the sub informationverification step, it is judged whether the sub information has beenrecorded normally or not by comparing a correlation value with apredetermined threshold, the correlation value indicating a correlationbetween the pseudo random number sequence and a signal to be verifiedthat is obtained by reproducing the recording area in which the subinformation is recorded.
 5. The optical disc defect management methodaccording to claim 4, wherein the sub information is recorded bydisplacing each of the recording marks of the main information on theoptical disc, according to the sub information correlation sequence, andthe correlation value is a correlation value between the pseudo randomnumber sequence and a direction in which said each of the recordingmarks is displaced.
 6. The optical disc defect management methodaccording to claim 5, wherein the sub information is recorded bydisplacing said each of the recording marks of the main information to aposition that is reached by advancing or delaying, by a minute amount,an edge of said each of the recording marks of the main information in atrack direction, according to the sub information correlation sequence.7. The optical disc defect management method according to claim 5,wherein the sub information is recorded by displacing said each of therecording marks of the main information to a position that is reached bydisplacing, by a minute amount, said each of the recording marks of themain information either toward an inner radius or an outer radius from acenter of a track in a radial direction, according to the subinformation correlation sequence.
 8. The optical disc defect managementmethod according to claim 2, wherein in the sub information verificationstep, it is judged, based on the recorded sub information and subinformation to be verified that is obtained by reproducing the recordingarea in which said sub information is recorded, whether said subinformation to be verified is recorded normally or not.
 9. The opticaldisc defect management method according to claim 2, wherein the subinformation includes an error correcting code and an error correctingand detecting code, and in the sub information verification step, it isjudged that sub information to be verified that is obtained byreproducing the recording area in which the sub information is recorded,has not been recorded normally in one of the following cases: where saidsub information to be verified cannot be corrected by the errorcorrecting code; and where an error correction is detected by the errorcorrecting and detecting code.
 10. The optical disc defect managementmethod according to claim 2, wherein in the defective area managementstep, the main information and the sub information are relocated andrecorded in the spare area, when it is regarded, in one of the maininformation verification step and the sub information verification step,that the recording area is the defective area related to the recordingof either the main information or the sub information.
 11. The opticaldisc defect management method according to claim 2, wherein in thedefective area management step, the main information and the subinformation are relocated and recorded in the spare area, when it isregarded, in the main information verification step and the subinformation verification step, that the recording area is the defectivearea related to the recording of the main information and the subinformation, only the main information is relocated and recorded in thespare area, when it is regarded in the main information verificationstep that the recording area is the defective area related to therecording of the main information and when it is regarded in the subinformation verification step that the recording area is not thedefective area related to the recording of the sub information, and onlythe sub information is relocated and recorded in the spare area, when itis regarded in the main information verification step that the recordingarea is not the defective area related to the recording of the maininformation and when it is regarded in the sub information verificationstep that the recording area is the defective area related to therecording of the sub information.
 12. The optical disc defect managementmethod according to claim 11, wherein in the defective area managementstep, information is registered into the defect management area, theinformation respectively indicating that the main information has beenrelocated and recorded and that the sub information has been relocatedand recorded.
 13. An optical disc recording apparatus for recording, onan optical disc, main information by forming optically-readablerecording marks and recording sub information by superimposing said subinformation on the main information, the optical disc recordingapparatus comprising: a verification unit operable to verify whether ornot the main information and the sub information have been recordednormally, every time a predetermined amount of main information and subinformation are recorded; and a defective area management unit operableto perform as follows when it is judged by the verification unit thatone of (i) the main information, (ii) the sub information, and (iii) themain information and the sub information, has not been recordednormally: relocate and record, in a predetermined spare area in theoptical disc, one of (i) the main information, (ii) the sub information,and (iii) the main information and the sub information, regarding that arecording area where the recording has been performed is a defectivearea related to a recording of one of (i) the main information, (ii) thesub information, and (iii) the main information and the sub information;and register, into a predetermined defect management area in the opticaldisc, information that associates the defective area with a replacementarea inside the spare area to which said defective area has beenrelocated.
 14. The optical disc recording apparatus according to claim13, wherein the verification unit includes: a main informationverification unit operable to judge whether or not the main informationhas been recorded normally and regard the recording area as thedefective area related to the recording of the main information, whenjudging that the main information has not been recorded normally; and asub information verification unit operable to judge whether the subinformation has been recorded normally or not and regard the recordingarea as the defective area related to the recording of the subinformation, when judging that the sub information has not been recordednormally.
 15. An optical disc reproduction apparatus for reading outmain information and sub information by reading optically-readablerecording marks from an optical disc, said sub information having beenrecorded by superimposing said sub information on the main information,the optical disc reproduction apparatus, comprising: a replacement areareproduction unit operable to reproduce one of (i) the main information,(ii) the sub information, and (iii) the main information and the subinformation from a replacement area where a defective area is replacedand recorded, when an area from which the main information and the subinformation are to be reproduced is said defective area related to arecording of one of (i) the main information, (ii) the sub information,and (iii) the main information and the sub information; and areproduction error judgment unit operable to judge that there is areproduction error in the main information and the sub information,while the area where said main information and said sub information arerecorded is being reproduced.
 16. The optical disc reproductionapparatus according to claim 15, wherein the replacement areareproduction unit judges whether the area from which the maininformation and the sub information are to be reproduced is thedefective area or not with reference to a defect management area insidethe optical disc where information that associates the defective areawith the replacement area is registered, and reproduces one of (i) themain information, (ii) the sub information, and (iii) the maininformation and the sub information from the replacement areacorresponding to the defective area, when judging that the area fromwhich the main information and the sub information are to be reproducedis the defective area.
 17. The optical disc reproduction apparatusaccording to claim 15, wherein the reproduction error judgment unitincludes: a main information reproduction error judgment unit operableto judge that there is a reproduction error of the main information; anda sub information reproduction error judgment unit operable to judgethat there is a reproduction error of the sub information, and thereproduction error judgment unit judges that the reproduction error is areproduction error of the area where the main information and the subinformation are recorded, when one of the main information reproductionerror judgment unit and the sub information reproduction error judgmentunit judges that there is a reproduction error.
 18. The optical discreproduction apparatus according to claim 17, wherein the subinformation includes an error correcting code and an error correctingand detecting code, and the sub information reproduction error judgmentunit judges that there is a reproduction error of the sub information inone of the following cases: where the sub information cannot becorrected by the error correcting code; and where an error correction isdetected by the error correcting and detecting code.
 19. An optical discreproduction method for reading out main information and sub informationby reading optically-readable recording marks from an optical disc, saidsub information having been recorded by superimposing said subinformation on the main information, the optical disc reproductionmethod, comprising: a replacement area reproduction step of reproducingone of (i) the main information, (ii) the sub information, and (iii) themain information and the sub information from a replacement area where adefective area is replaced and recorded, when an area from which themain information and the sub information are to be reproduced is saiddefective area related to a recording of one of (i) the maininformation, (ii) the sub information, and (iii) the main informationand the sub information; and a reproduction error judgment step ofjudging that there is a reproduction error in the main information andthe sub information, while the area where said main information and saidsub information are to be recorded is being reproduced.
 20. A programfor carrying out defect management of an optical disc on which maininformation is recorded by forming optically-readable recording marks,and on which sub information is recorded by superimposing said subinformation on the main information, the program causing an optical discrecording apparatus to execute the steps included in the optical discdefect management method according to claim
 1. 21. A program for readingout main information and reading out sub information which has beenrecorded by superimposing said sub information on the main information,by reading optically-readable recording marks from an optical disc, theprogram causing an optical disc reproduction apparatus to execute thesteps included in the optical disc reproduction method according toclaim
 19. 22. An optical disc on which main information is recorded byforming optically-readable recording marks, and on which sub informationis recorded by superimposing said sub information on the maininformation, wherein there is a defective area where one of (i) the maininformation, (ii) the sub information, and (iii) the main informationand the sub information has not been recorded normally, and one of (i)the main information, (ii) the sub information, and (iii) the maininformation and the sub information that is supposed to be recorded insaid defective area is relocated and recorded in a predetermined sparearea in the optical disc, and information is recorded in a predetermineddefect management area in the optical disc, the information associatingthe defective area with a replacement area inside the spare area towhich said defective area is relocated.
 23. The optical disc accordingto claim 22, wherein the information that associates the defective areawith the replacement area includes information that respectivelyindicates that the main information has been relocated and recorded andthat the sub information has been relocated and recorded.